How are blood clots diagnosed?

The initial step in making the diagnosis of a blood clot is obtaining a patient history. The blood clot itself does not cause a problem. It's the location of the blood clot and its effect on blood flow that causes symptoms and signs. If a blood clot or thrombus is a consideration, the history may expand to explore risk factors or situations that might put the patient at risk for forming a clot.

Venous blood clots often develop slowly with a gradual onset of swelling, pain, and discoloration. Symptoms of a venous thrombus will often progress over hours.

Arterial thrombi occur as an acute event. Tissues need oxygen immediately, and the loss of blood supply creates a situation in which symptoms begin immediately.

There may be symptoms that precede the acute artery blockage, that may be warning signs of the potential future complete occlusion of the blood vessel.

Patients with an acute heart attack (myocardial infarction) may experience angina in the days and weeks prior to the heart attack.

Patients with peripheral artery disease may have pain with walking (claudication), and a TIA (transient ischemia attack, mini-stroke) may precede a stroke.

Physical examination can assist in providing additional information that may increase the suspicion for a blood clot.

Venous thrombi may cause swelling of an extremity. It may be red, warm, and tender; sometimes the appearance is difficult to distinguish from cellulitis or an infection of the extremity. If there is concern about a pulmonary embolus, the clinician may examine the lungs, listening for abnormal sounds caused by an area of inflamed lung tissue.

Arterial thrombus symptoms are much more dramatic. If a leg or arm is involved, the tissue may be white because of the lack of blood supply. As well, it may be cool to touch and there may be loss of sensation and movement. The patient may be writhing in pain.

Arterial thrombus is also the cause of heart attack (myocardial infarction) and stroke (cerebrovascular accident) and their associated symptoms. Continue Reading

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.